Methods and articles in having a fringed microprotrusion surface structure

Abstract

Composite articles and a method for making the same, wherein the articles include at least two bodies that are attached at an interface that includes a fringed microprotrusion surface structure. The method generally includes the steps of providing a first body that includes a fringed microprotrusion surface structure on one or more surfaces; and attaching to the first body, a second body for defining the interface that includes at least a portion of the fringed microprotrusion surface structure.

1 . A method for making a composite article, comprising the steps of: 
 a. providing a first body that includes a fringed microprotrusion surface structure; and    b. attaching to the first body, a second body for defining an interface that includes at least a portion of the fringed microprotrusion surface structure.    
     
     
         2 . The method of  claim 1 , wherein the fringed surface structure is characterized by a plurality of generally conical microprotrusions that project from a surface of the first body.  
     
     
         3 . The method of  claim 2 , wherein the generally conical microprotrusions are generally closed at their distal ends.  
     
     
         4 . The method of  claim 2 , wherein the generally conical microprotrusions include a curved distal end for defining a hook.  
     
     
         5 . The method of  claim 2 , wherein the generally conical microprotrusions generally have an aspect ratio (height to diameter) in the range of about 0.5:1 to 7:1.  
     
     
         6 . The method of  claim 5 , wherein the generally conical microprotrusions generally have an aspect ratio (height to diameter) in the range of about 2:1.  
     
     
         7 . The method of  claim 2 , wherein over at least 20% by area of the fringed surface portion of the first body, the generally conical microprotrusions are present in a concentration of at least about 225 protrusions per cm 2 .  
     
     
         8 . The method of  claim 2 , wherein the generally conical microprotrusions have an average diameter of from about 40 to about 350 microns.  
     
     
         9 . The method of  claim 2 , wherein the generally conical microprotrusions have an average height of about 25 to 500 microns.  
     
     
         10 . The method of  claim 2 , wherein the first body is plastic and the polymer of the first plastic body includes at least 40 wt % of a polyolefin polymer.  
     
     
         11 . The method of  claim 7 , wherein the first body is plastic and the polymer of the first plastic body includes at least 60 wt % of a polypropylene.  
     
     
         12 . The method of  claim 11 , wherein the first body is plastic and the polymer of the first plastic body consists essentially of a polypropylene.  
     
     
         13 . The method of  claim 2 , wherein the first body includes glass fiber reinforcement.  
     
     
         14 . The method of  claim 13 , wherein the first body includes long glass fiber reinforcement.  
     
     
         15 . The method of  claim 2 , wherein the first body is plastic and the first plastic body has a melt index per ASTM D1238 of at least about 20.  
     
     
         16 . The method of  claim 2 , wherein the second body is plastic and includes at least 40 wt % of a polyurethane foam, and further wherein the attaching step occurs when the polyurethane is foamed.  
     
     
         17 . The method of  claim 1 , wherein the step of providing a first body includes injecting molding or die casting the first body.  
     
     
         18 . The method of  claim 1 , wherein cohesive failure of the second body is observed upon separating the first body from the second body.  
     
     
         19 . The method of  claim 1 , wherein the resulting lap shear, or peel strength observed upon separating the first body from the second body is at least three times greater than that which would be observed if compared with a lap shear, or peel strength of a joint formed by a comparable structure that omits the fringed surface structure from the first body, substituting in its place a surface that has only been mechanically roughened to increase surface area by 40%.  
     
     
         20 . The method of  claim 1 , wherein the composite article is an instrument panel that is substantially free of an adhesion promoter between the first body and the second body.